Transformation and accumulation of selenium nanoparticles in the soil-rice system under different water management

The effects of foliar application of selenium nanoparticles (SeNPs) on rice growth and Se accumulation has been studied, but soil application of SeNPs on rice Se uptake and its transformation in soil remain limited. Water management is a key agronomic practice in rice cultivation. This study examined the effects of varying water management regimes (continuous flooding [CF] and alternating wet and dry [AWD]) and concentrations (0, 0.5, and 2 mg·kg^-1) of SeNPs on rice growth, Se accumulation, soil Se transformations, and bacterial communities in a pot experiment. Results revealed that soil-applied SeNPs enhanced growth and Se accumulation of rice. Compared with CF treatment, AWD treatment promoted the accumulation of Se in rice but decreased leaf photosynthetic activity and Se content in leaf organelles. After soil application of SeNPs, soil Se fractions were dominated by organic-bound Se (OM-Se) and residual Se (RES-Se). SeNPs in soil have higher transformation rate at low concentration and AWD water management. Water management and SeNP application jointly affected the rhizosphere bacterial community structure. 2 mg·kg^-1 SeNPs increased Chloroflexi abundance by 12.3 % and 30.6 % in CF and AWD water management, respectively. The increase in Chloroflexi abundance facilitated the conversion of stable Se fractions (OM-Se and RES-Se) to active Se fractions (soluble Se and carbonate bound Se) in soil. The present study may provide theoretical support for Se biofortification in rice grown in Se-deficient regions.